A 36-year-old primigravid woman comes to the office at 15 weeks gestation due to vaginal bleeding
. This morning, she woke up and noticed blood in her underwear. She has also had severe morning nausea that has been worsening, resulting in multiple episodes of vomiting throughout the day for the past week. She states it has been difficult to keep down anything she eats or drinks. She denies shortness of breath
, changes in vision, or chest pain. She does not use tobacco, alcohol
or illicit drugs. Current temperature is 37.0°C (98.6°F), pulse
is 100/min, and blood pressure
is 145/85 mmHg. On physical examination, a 15-week-size uterus
and bilateral adnexal masses are palpated on bimanual examination. Laboratory tests show hCG concentrations of 110,000 mIU/mL. TSH is 0.1 μU/mL. Which of the following is the most likely diagnosis?